//nav
if(document.images){
  var main = new Image(); main.src = "Images/vars1.jpg";
  var img1 = new Image(); img1.src = "Images/vars2.jpg";
  var img2 = new Image(); img2.src = "Images/vars3.jpg";
  var img3 = new Image(); img3.src = "Images/vars4.jpg";
 }
function change(imageName){
  if(document.images){ document['main'].src = eval(imageName + ".src"); }
}
function changeBack(){
  if(document.images){ document['main'].src = main.src; }
}